I. Field of the Disclosure
The technology of the disclosure relates generally to a signaling protocol for use on a communication bus, and particularly for a radio frequency front-end control interface (RFFE) bus.
II. Background
Computing devices have become increasingly common in modern society. Mobile phones are among the more common computing devices. While such devices may initially have started out as simple devices that allowed audio communication through the Public Land Mobile Network (PLMN) to the Public Standard Telephone Network (PSTN), they have evolved into smart phones capable of supporting full multimedia experiences as well as supporting multiple wireless protocols. Even within the cellular wireless protocols, mobile phone radios have developed into highly complex, multi-band, and multi-standard designs that often have multiple radio frequency (RF) signal chains. Every component in the RF signal chain has to be in the desired configuration at any given time, or the system will fail. Therefore, accurate timing, triggers, and speed are all necessary.
As further explained on the MIPI Alliance® website, “[t]he MIPI Alliance Specification for RF Front-End Control Interface (RFFE) was developed to offer a common and widespread method for controlling RF front-end devices. There are a variety of front-end devices, including Power Amplifiers (PA), Low-Noise Amplifiers (LNA), filters, switches, power management modules, antenna tuners and sensors. These functions may be located either in separate devices or integrated into a single device, depending on the application. The trend in mobile radio communications is towards complex multi-radio systems comprised of several parallel transceivers. This implies a leap in complexity of the RF front-end design. Thus, the RFFE bus must be able to operate efficiently in configurations from the simplest one Master and one Slave configuration to, potentially, multi-Master configurations with tens of Slaves.”
In devices where there are multiple masters on an RFFE bus, the RFFE protocol allows ownership transfer that introduces unavoidable latency. Aggravating the latency issue is that the latency may not be a fixed latency because of collision unpredictability. Such unpredictable latency may interfere with the performance requirements set forth by the various wireless protocols being served by the RF front-end. Accordingly, there is a need for a reduced latency hand-off approach.